1. Field of the Invention
The present invention relates to a balancer board for a back light device.
2. Description of the Related Art
Nowadays, liquid crystal display devices using liquid crystal panels are being widely used in various industrial fields. In one of the liquid crystal display devices mentioned above, there is adopted a structure in which a backlight device is provided on the rear surface of the liquid crystal panel and the liquid crystal panel is irradiated with light from the backlight device. As the backlight devices, cold cathode fluorescent lamps (CCFLs) and hot cathode fluorescent lamps (HCFLs) are frequently used. A backlight system using an existing inverter has a configuration as shown in FIG. 5, in which current supplied from an inverter board 100 is shunted using a balancer board 200 so as to be supplied to each of fluorescent tubes having negative resistances such as cold cathode fluorescent lamps (CCFL(1) to CCFL(20)) or hot cathode fluorescent lamps (not shown). In the example shown in FIG. 5, the floating capacitance between a high voltage pattern and a low voltage pattern or Jin coils disposed on one surface of the balancer board 200 has a value different from that of the floating capacitance between a high voltage pattern and a low voltage pattern or Jin coils disposed on the other surface of the balancer board 200. That is, the floating capacitance between one input of the fluorescent tube and the ground (GND) differs from the floating capacitance between the other input of the fluorescent tube and the ground (GND). In the example shown in FIG. 5, an inverter circuit is driven to generate AC power of several kVrms and several tens of kHz. Thus, the influence of the difference between the floating capacitances of each fluorescent tube is so great that tube currents flowing through respective fluorescent tubes and open-circuit voltages which may be necessary to start respective florescent tubes become unbalanced among the fluorescent tubes. Note, in the specification, the open-circuit voltage is a voltage of a value equal to or higher than a certain fixed value which may be necessary to start a fluorescent tube (see, for example, Japanese Laid-Open Patent Publication No. 2005-353572).